It's different for everyone.  Get fitted by a Titleist rep.

It depends on how you swing...mostly aldila RIP (if looking for stock shaft) if not, Diamana WhiteBoard is a good one..

That's kind of an open ended question.  The 8.5 D3 head potentially gets the most roll.  The lowest spinning shafts are typically heavy like the Fujikura Pro 95, the Diamana Ahinas, and the shaft I'm currently testing, the Aldila RIP series.

Ryan, I bought the project x, after market shaft. Hit it 400 times at golfsmith, D2,460. I'm an old guy, 63. Hit it staight everytime during December and January when I tested the driver out. Perfectly straight, set on a1. Thanks J.J.

Awesome!  Happy driving!